It has long been known to protect parts of the body against cold by covering them with garments to provide insulation. For example, in the case of humans, the hands may be covered with mitts or gloves, the feet may be covered with socks and boots, the neck and face may be covered with a scarf, and the ears may be covered with earmuffs, a headband or a hat. The paws of domestic animals may be similarly covered, and pet dogs are often outfitted with boots adapted to their paws to protect against snow and cold during winter walks.
It is also known to use exothermic heating packs in combination with garments such as mitts and gloves. Exothermic heating packs utilize an exothermic chemical reaction to release heat, and can be placed inside a garment such as a glove to heat the body part inside. Some garments such as gloves include special pockets for receiving exothermic heating packs. Exothermic heating packs may be either reusable or of the single-use type.
One type of reusable exothermic heating pack relies on the exothermic crystallization of supersaturated solutions, which is initiated by using a small metal disk to generate nucleation and begin crystallization. Sodium acetate is typically used as the supersaturated solution. By heating the exothermic heating pack after use (e.g. in hot water) until the contents are fluid and then letting it cool, it can be “recharged” for reuse.
One type of single-use exothermic heating pack, referred to herein as an “iron oxidation heating pack”, contains cellulose, iron, vermiculite, water, activated carbon and salt in a porous container. The vermiculite serves as a water reservoir, the activated carbon assists in even heat distribution, and the salt acts as a catalyst. This type of exothermic heating pack is air-activated and, when it is exposed to air, heat is generated by the exothermic oxidation of the iron. These exothermic heating packs are therefore sold in airtight packages and opened when heat is desired.
Examples of gloves which may be used with exothermic heating packs include those taught by U.S. Pat. No. 2,792,827 to Gravin et al., U.S. Pat. No. 4,587,672 to Madnick et al., U.S. Pat. No. 5,035,003 to Rinehart and U.S. Patent Application Publication No. 2010/0095947 in the name of Gellis. Gellis also teaches an exothermic heating pack having a partial hand shape that can be held to the hand by way of caps that receive a user's fingertips and thumbtip and a strap extending across the palm, or by way of a catch that allows the user's fingers to be inserted between the catch and the heating element.